No idea...  but that doesn't change the fact that attach rates are the number of games that are sold per console, right? If that's the case, to get the real attach rates of a system you have to compare numbers sold. I'm not sure about this either, but if developers make money off of royalties or the number of games sold, then it would be relevant to only assess sold-through rates; otherwise it would be the retailers that are technically paying the developers their commission!

But again - I'm not sure - perhaps somebody could clarify? 

According to http://ce.seekingalpha.com/article/40770 , the Gamecube sold 21.59 million systems and 206 million games.

That works out to a 9.54 attach rate.

The article has a lot of other numbers, but I don't see anything useful for figuring out non-Nintendo attach rates. (N64 got 6.81, DS had gotten 4.56 through March, NES/SNES/N64 collectively got 5.5, and GB/GBA got 4.4.)

But in the long term, shipped = sold, so it's kind of irrelevant, isn't it? And with the PS2 being seven years old, the number of games sitting on shelves in video game stores would be rather small compared to total software shipments.

Here are some Sony links. The PS2's shipped attach rate is around 10.5.

http://www.scei.co.jp/corporate/data/bizdatasoft_e.html

http://www.scei.co.jp/corporate/data/bizdataps2_e.html

Approximately 1,240 million shipped for software and 117.89 million for hardware.

I'm not sure - and I would like to know with a certain degree of certainty  - hence my asking if anyone could shed some light on the matter.

I do think shipped vs sold are different - it's even on the homepage of VGChartz touted as the site's uniqueness, so I do think it's still relevant.

If only someone could clarify how game sales really works...

Interesting, so the 360 and the Gamecube have had the 2 highest attach rates of all time. The Gamecube one is even more interesting, as Nintendo software sold incredibly well despite it's small install base. If Nintendo software leads to such high attach rates on a system like the Gamecube, can we expect some pretty crazy sales numbers for these games on the Wii? Will the core gamer attach rate be good on the Wii, but the casual attach rate bring that down? It's a very interesting situation.

naz - I would say that the Wii's attach ratio even in the end won't be near GCs.

Merely because the GC was very hardcore in its user base - as most of the people that owned it owned it for the big-N IPs and responded by buying alot (Windwaker, Zelda:TP, SMS, ect), whereas the Wii will have a much broader base, and be more difficult, as your dealing with a more broad base of people deciding to buy more or less games depending on their buying habbits.